So basically I'm wondering if i require anything extra to power my graphics card. I received a power cable with the graphics card which converts two pci-e plugs into the 8 prong required for the graphic card. my power supply only has two pci-e cords coming from my power supply. I plugged one into the graphics card and one into the power cable but it still has one unused part. do i have to have both parts of the power cable connected or only one?